The first objective of this research is to develop and test a physically simple model for the orientational energy of hydrogen bonds which takes non-additivity into account. Various evidence indicates that the latter may play an important role in determining orientations. A potential composed of multipole and induced-dipole terms combined with dispersion and repulsion terms is being tested against extended basis set quantum mechanical dimer and the non-additive polymer calculations on water. The second objective is to develop and test simplification which will give an appropriate model for calculations of more complex properties of interest such as the properties of bulk water, the surface-structure of water droplets, the structure in the neighborhood of polar surfaces (such as cell walls), etc.